You Do Need power plug adapter while traveling from Nepal to Niger.

Here is Why You Need An Adapter

The outlet and plug type used in Niger are C, D, E and F and in Nepal are C, D and M. This is how they look like.

Nepal

In Nepal, outlets of type C, D and M are in use.

Type C

Type D

Type M

Niger

In Niger, outlets of type C, D, E and F are in use.

Type C

Type D

Type E

Type F